This invention relates generally to a method and apparatus for determining a smoothness of a pavement and, more particularly, to a method and apparatus for determining a change in elevation of a pavement that is indicative of a profile of the pavement.
It is common to analyze and determine the quality of a pavement in terms of a profile of the pavement; that is, how much the pavement changes in elevation for a given distance. For example, it may be desired to maintain a pavement profile that does not exceed plus or minus 10 mm for every 2500 mm sampled distance. A profile which exceeds this value would require work to be performed on the pavement to reduce excessive deviations from a smooth pavement profile. The excessive profile may be caused during new construction, or perhaps during a re-paving operation.
Typically, special machines, known as profilographs, are used to determine the profile of the pavement. A typical profilograph has a leading wheel toward the front end of the machine, a trailing wheel toward the back end of the machine which is separated by a relatively long distance from the leading wheel, and a measuring wheel at some point near the middle of the machine. The measuring wheel is configured to measure deviations of the pavement as the machine moves. The linear changes in elevation indicate the profile.
During paving operations, the paving work is completed, then the profilograph traverses the pavement recording the profile, including any deviations which exceed allowable tolerances. The locations which did not meet standards would then require additional work, including the possibility of removing and replacing the new pavement.
The above described process is very costly and inefficient, since it requires a dedicated machine which determines problem areas after the paving work is completed, and the possibility exists that some of the work will need to be repeated. It is desired, therefore, to be able to determine a profile of a pavement during real time, i.e., as the work is being performed. For example it would be desirable to be able to determine a profile and correct any out of tolerance areas during a work function such as compaction of the pavement.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention a method for determining a profile of a pavement is disclosed. The method includes the steps of determining a slope of a mobile machine as the mobile machine traverses the pavement, and determining a change in elevation of the pavement as a function of the slope and a distance from a first ground engaging member on the mobile machine to a second ground engaging member on the mobile machine, the change in elevation being indicative of a profile of the pavement.
In another aspect of the present invention an apparatus for determining a profile of a pavement is disclosed. The apparatus includes a mobile machine having a first ground engaging member and a second ground engaging member, the first ground engaging member being a known distance from the second ground engaging member, a slope determining system located on the mobile machine, and a controller located on the mobile machine for receiving a signal indicative of a change in slope from the slope determining system, and responsively determining a change in elevation of the pavement as a function of the change in slope and the distance between the first and second ground engaging members, the change in elevation being indicative of a profile of the pavement.
In yet another aspect of the present invention a method for determining a deviation from a profile specification of a pavement is disclosed. The method includes the steps of establishing a maximum allowable change in slope of the pavement, the maximum allowable change in slope being a function of a maximum allowable profile deviation of the pavement, the maximum allowable profile deviation being indicative of the profile specification, monitoring a change in slope of a mobile machine as the mobile machine traverses the pavement, and determining a condition of the change in slope being greater than the maximum allowable change in slope.